1. Field of the Invention
This invention relates to hydraulic couplings. More particularly, it relates to undersea hydraulic couplings used in systems which employ electrical bonding of components.
2. Description of the Related Art
A wide variety of undersea hydraulic couplings are available. Some couplings employ metal seals. Examples of undersea hydraulic couplings having metal seals include U.S. Pat. No. 4,694,859 for “Undersea hydraulic coupling and metal seal” U.S. Pat. No. 4,817,668 for “Integral metal seal for hydraulic coupling” U.S. Pat. No. 4,884,584 for “Internally preloaded metal-to-metal seal hydraulic connector” U.S. Pat. No. 5,029,613 for “Hydraulic coupler with radial metal seal” U.S. Pat. Nos. 5,099,882 and 5,203,374 for “Pressure balanced hydraulic coupling with metal seals” U.S. Pat. No. 5,284,183 for “Hydraulic coupler with radial metal seal” U.S. Pat. No. 5,339,861 for “Hydraulic coupling with hollow metal o-ring seal” U.S. Pat. No. 5,355,909 for “Undersea hydraulic coupling with metal seals” U.S. Pat. No. 5,979,499 for “Undersea hydraulic coupling with hollow metal seal” U.S. Pat. No. 6,962,347 for “Metal backup seal for undersea hydraulic coupling” and U.S. Pat. No. 7,021,677 for “Seal retainer with metal seal members for undersea hydraulic coupling” all to Robert E. Smith III and assigned to National Coupling Company of Stafford, Tex.
Other undersea hydraulic couplings employ only “soft seals”—i.e., non-metal seals that are typically formed of an elastomeric polymer (“elastomer”) or an engineering plastic capable of being machined such as polyetheretherketone (“PEEK”) or DELRIN® acetal resin.
By way of example, U.S. Pat. No. 6,123,103 discloses a pressure balanced hydraulic coupling for use in undersea drilling and production operations. The coupling has radial passages connecting between the male and female members such that fluid pressure is not exerted against the face of either member during coupling or uncoupling. The female member has a split body with a first part and a second part, each having a longitudinal passage and a radial fluid passage. A radial seal is positioned on the junction between the first and second parts of the female member body to facilitate removal and replacement of the radial seal when the split body is disassembled. The male member may be inserted through the first and second parts of the female coupling member, thereby establishing fluid communication between the coupling members in a direction transverse to the coupling member bores.
U.S. Pat. No. 6,179,002 discloses an undersea hydraulic coupling having a radial pressure-energized seal with a dovetail interfit with the coupling body. The seal has a pair of flexible sealing surfaces for sealing with the male and female coupling members and a cavity therebetween that is exposed to fluid pressure in the coupling. The outer circumference of the seal has a dovetail interfit between inclined shoulders in the female member bore and on a seal retainer that holds the seal in the bore.
U.S. Pat. No. 6,575,430 discloses an undersea hydraulic coupling member having a ring-shaped seal with multiple scaling surfaces extending radially inwardly therefrom. The multiple sealing surfaces help guide the probe of the male coupling member into the female member without the risk of drag or galling of the receiving chamber. The seal has an interfit with reverse inclined shoulders in the female member to restrain the seal from moving radially inwardly due to vacuum or low pressure. Attention is invited in particular to the embodiments shown in FIGS. 8 and 9 of this patent.
U.S. Pat. No. 6,923,476 discloses a floating seal for an undersea hydraulic coupling member that is moveable radially to seal with the male coupling member even if there is some misalignment with the female coupling member. The floating seal is restricted from axial movement within the female coupling member receiving chamber. The floating seal may seal with the female coupling member.
U.S. Patent Application Publication No. US 2005/0029749 discloses an undersea hydraulic coupling member having a bore liner that protects the coupling members from galling during assembly or disassembly. The bore liner is removable from the bore of a female undersea hydraulic coupling member. The bore liner may be integral with a seal section that may seal with a male undersea hydraulic coupling member. The bore liner also may have an outer diameter configured to engage and interlock with the bore in which the bore liner is positioned. In certain embodiments, the bore liner is fabricated from PEEK.
Bonding refers to the connection of all metal objects such as pipes, conduits and structural steel together to form an equipotential zone. Often, bonding includes an electrical connection to earth (ground potential). To remove dangerous voltage from ground faults, metal parts of electrical raceways, cables, enclosures, and equipment must be bonded to an effective ground-fault current path with an equipment grounding (bonding) conductor of a suitable type.
Equipment bonding provides an effective electrically continuous path in an effort to conduct stray voltage/current safely to ground. The National Electrical Code also states that it is good practice to bond all metallic systems and objects.
Bonding requirements and tests are intended to ensure that a system or facility is free from such hazards as electrical shock and static discharge. In addition, bonding requirements provide for reliable fault clearing paths and the suppression of electromagnetic interference (EMI). A typical bonding requirement might require that the chassis or structure of all equipment which is operating from a common power source shall be bonded such that maximum electrical fault currents can be conducted without creating a thermal or electrical hazard and that electrical bonds between all equipment shall be made to minimize differences in potential.
Bonding reduces electrostatic EMI by preventing the build-up and subsequent discharge of static charges. Bonding prevents surfaces from electrically resonating and radiating EMI. Bonding eliminates harmonic EMI by eliminating current rectification at contact surfaces. Bonding assures that all parts are at the same potential which prevents higher RF current flow in one part of the structure than another.
Cathodic protection is a technique used to control the corrosion of a metal surface by making that surface the cathode of an electrochemical cell. Cathodic protection systems are most commonly used to protect steel structures, water and fuel pipelines and storage tanks; steel pier piles, ships, offshore oil platforms and onshore oil well casings. Cathodic protection is an effective method of preventing stress corrosion cracking.
Galvanic or sacrificial anodes are made in various shapes typically using alloys of zinc, magnesium and aluminum. The electrochemical potential, current capacity, and consumption rate of these alloys are advantageous for cathodic protection.
Galvanic anodes are designed and selected to have a more negative electrochemical potential than the metal of the structure (typically steel). For effective cathodic protection, the potential of the steel surface is polarized more negative until the surface has a uniform potential. At that stage, the driving force for the corrosion reaction is halted. The galvanic anode continues to corrode, consuming the anode material until eventually it must be replaced. The polarization is caused by the current flow from the anode to the cathode. The driving force for the cathodic protection current flow is the difference in electrochemical potential between the anode and the cathode.
For larger structures, galvanic anodes cannot economically deliver enough current to provide complete protection. Impressed Current Cathodic Protection (ICCP) systems use anodes connected to a DC power source (a cathodic protection rectifier). Anodes for ICCP systems may be tubular and solid rod shapes or continuous ribbons of various specialized materials. These include high silicon cast iron, graphite, mixed metal oxide, platinum and niobium coated wire and others. In any cathodic protection system, bonding is required to provide a current path and achieve a uniform surface potential.
Electrical bonding is not always assured in an hydraulic coupling. This is especially true if the coupling has only soft seals and no metal seals since the male probe may not make metal-to-metal contact with the body of the female member. Not all couplings employ poppet valves with their associate actuators which contact one another when the coupling is made up. Moreover, many hydraulic fluids are dielectrics—an electrical insulator—and a thin film of hydraulic fluid on the surface of a part may prevent electrical continuity with an adjacent part.
To remedy this situation, designers often specify bonding straps to provide a low-impedance electrical pathway from one side of a coupling to the other. Such straps may be connected to the coupling bodies with clamps or, in some cases, machine screws which fit into threaded holes in the coupling body. These devices however, significantly increase the work required to make up and disconnect a hydraulic coupling. Particularly in the undersea environment where such work must be performed by remotely operated vehicles (ROVs) this is a significant disadvantage. What is needed is a hydraulic coupling which automatically electrically bonds the male and female members together upon make up. The present invention solves this problem.